Recently high-yield pulps have come to be commonly used as a main material for newsprint paper, magazine paper and low-grade printing paper. Typical examples of the high-yield pulp are refiner groundwood pulp (RGP) prepared by refining softwood chips with a disc refiner, thermomechanical pulp (TMP) prepared by treating heat-softened softwood chips with a disc refiner under a pressurized condition, chemiground pulp (CGP) and semichemical pulp (SCP) prepared by refining hardwood chips with a disc refiner after they are treated with sodium hydroxide or sodium sulfite.
These high-yield pulps have a problem that they are mechanically refined with a disc refiner in their preparation and demand more electric power than chemical pulps (CP), which is the most impedimental problem involved in the use of high-yield pulps. In the case of CP as well, beating of the pulp with a refiner is also normally carried out prior to the papermaking step for accelerating the swelling of the fibers and enhancing the bonding strength between the fibers. Here consumption of a large amount of energy is also a problem to be solved.
Studies in search of the additives useful for reducing power consumption in refining or beating of pulp have been conducted from the viewpoint of energy-saving. One of such studies, for instance, proposed direct addition of a dye Congo Red to the pulp, which remarkably reduces the power consumption in the beating. The use of Congo Red, however, is impracticable since it dyes the pulp red.